1. Field of the Invention
The present invention relates to a printing system in which plural printing apparatuses are connected to each other to execute printing in cooperation therewith to print out data.
2. Description of the Related Art
Recently, there has been proposed an image processing apparatus configured to print using transparent toner (clear toner), which is a kind of special recording agents.
The whole surface coat method which prints the whole printable area of a printing paper with clear toner can provide the whole paper surface with glossiness like a photograph by printing the whole surface of the paper with the clear toner after printing with color toner like CMYK toner.
The partial surface coat method of printing a specified section of the printable area of the printing paper with the clear toner can provide a printed paper partially with glossiness or a decorative effect by printing the paper with the clear toner after printing with the color toner.
Printing with the clear toner enables a variety of expressions by adding a value to an output print.
To execute printing with the clear toner, a system for transferring color toner like the CMYK toner and the clear toner onto a printing paper and fixing the color toner image and the clear toner image on the printing paper at a time is built into an image processing apparatus. Using this image processing apparatus, printing using the clear toner is executed.
However, a problem occurs when adding a configuration for printing with the clear toner. For example, a problem about a loading amount of the toner occurs. More specifically, the image processing apparatus has a limitation (restriction on the total loading amount) of a toner amount which can be fixed in a unit area of the printing paper by a single fixing action. Thus, in an area where a large amount of the CMYK toner is used, no sufficient amount of the clear toner can be used because the total toner amount within the loadable amount is restricted.
To solve this problem, Japanese Patent Application Laid-Open No. 2008-145595 discusses an image processing system combining an image processing apparatus for printing with the color toner, and another image processing apparatus for printing with the clear toner, which are connected to each other to produce a print output with the clear toner. For example, for a user who wants to use the clear toner, an image processing system including an image processing apparatus (apparatus on the former stage) is proposed which executes transferring and fixing of an image with the color toner and another image processing apparatus (apparatus on the latter stage) which executes transferring and fixing of the image with the clear toner, which are connected to each other. In such a configuration, both the CMYK toner and the clear toner can be sufficiently used in a printing target.
In this printing system, an output product from the apparatus on the former stage (hereinafter referred to as former stage apparatus) is input to the apparatus on the latter stage (hereinafter referred to as latter stage apparatus) just as it is. At this time, it is ideal that no misregistration occurs in plane when the both images are printed on an identical paper. However, there is a high possibility that the misregistration in plane may occur on the identical paper because the two printing apparatuses are used.
More specifically, as compared to a case of forming an image with a single conventional printing apparatus, the misregistration is conspicuous in an image output by such plural printing apparatuses connected to each other. For example, when printing with a printing system including the apparatus for printing with the CMYK toner on the former stage and the anther apparatus for printing with the clear toner on the latter stage, which are connected to each other, sometimes the misregistration may be highly noticeable between the color image printed with the CMYK toner and the clear image printed with the clear toner.
Further, another problem is that it is difficult to correct the misregistration compared with a conventional printing apparatus. Although, in the case of a single printing apparatus, the misregistration can be automatically corrected by equipping the printing apparatus with an internal sensor or the like, the misregistration which occurs between separate printing apparatuses cannot be corrected using the internal sensors provided in each apparatus.
Additionally, the misregistration occurs each time when a combination of the former stage apparatus and the latter stage apparatus is changed. Thus, the frequency of correcting the misregistration increases. Yet still another problem is that if existing printing apparatuses are connected to each other to configure this system, it is difficult to add later a means for correcting the misregistration like a sensor to the existing apparatus. Further, from technical viewpoints, it is difficult to avoid the misregistration in printing position between two printing apparatuses completely. As a result, it is possible that the misregistration may be left on the identical printing paper even if the correction is carried out using some means. Despite the above-stated problems, sometimes, alignment between the color image and the clear image is not necessary depending on use application of a final output product or a decorative effect with the clear toner which a user expects. For example, in a case of the “whole surface clear coating” where the whole printable area of a printing paper on which color images are printed is coated with the clear toner, the visual effect of the printed image is little influenced even if some extent of misregistration exists.
Further, in the case of using two printing apparatuses connected to each other, if the latter stage apparatus internally contains a structure for printing the color toner, the latter stage apparatus can execute a printing procedure alone. Thus, if the two printing apparatuses are connected to each other but do not need to be used at the same time to achieve a printing procedure depending on a given printing procedure condition, an operation mode of executing that procedure with only the latter stage apparatus is conceivable. Such a case occurs where a high gloss as a visual effect is not desired, so that a large amount of the clear toner is not applied, where there are few places on which the clear toner needs to be applied, where there are few overlaps between the color image portion and the clear image portion or where no high quality is demanded. In such a case, by printing the color image and the clear image with only the latter stage apparatus, the misregistration, which may occur when using two printing apparatuses connected to each other, can be avoided.